CRPS (full name Complex Regional Pain Syndrome) is the new World Health Organisation name for RSD, Reflex Sympathetic Dystrophy and its definition is subdivided into CRPS type I and CRPS type II.

CRPS is pain that develops after a relatively minor injury to an arm or leg, but lasts much longer and is much more severe than would normally be expected.

CRPS II is diagnosed when pain can be traced to an identifiable nerve injury. This condition is sometimes called Causalgia (literally "hot pain").

CRPS I is diagnosed when similar symptoms are manifested but there is no identifiable nerve injury. This is intended to cover the strict definition of Reflex Sympathetic Dystrophy (RSD).

For patients the difference is academic because the symptoms are similar, especially the pain, and the same range of treatments are offered. Note also that a "Type I" diagnosis indicates that no nerve injury has been identified - which is not the same as saying that no nerve injury exists.
Derrick Phillips - Editor of RSD Alert

Complex Regional Pain Syndrome (Chronic Neuropathic (sometimes called Neurogenic) Pain, RSD, Causalgia, is characterised by a collection of symptoms and there is evidence that shows that these types of symptoms were
being observed in patients by Doctors over 150 years ago. So it isn't new - it's just that these symptoms have been given lots of different names (Sudeks Atrophy, Reflex Sympathetic Dystrophy, Causalgia, Chronic Traumatic Oedema, Shoulder Hand Syndrome, Steinbroker Syndrome, Sympathalgia, Sympathetic Overdrive Syndrome - and more!).

In 1992 an International Team of Doctors introduced a new name that was an attempt to try encompass and simplify the naming of Chronic Neuropathic Pain disorders. They called this 'Complex Regional Pain Syndrome' (CRPS) - and gave it two parts:

CRPS Type 1 and CRPS Type 2.
CRPS Type 1 - (Reflex Sympathetic Dystrophy).
Is caused by - a simple injury, football, athletics, falling over - perhaps a fracture, perhaps a minor operation. A nerve or tissue gets injured - and the resulting pain is totally disproportionate to the injury (a severe intense 'Burning' pain that is not relieved by strong pain killers). The pain may go on for months, even years long after the initial injury has healed. The pain is often much worse at night - and not just because of tiredness. The symptoms that can occur are:

Intense burning pain - this may radiate to previously unaffected areas. Numbness, sensation disturbances on the skin - this may also radiate to previously unaffected areas.
Loss of control of the affected limb or another previously unaffected limb -
weakness, numbness.
An occasional cold or cool affected limb.
Swelling of the affected limb.
Headaches.
Nausea.
Insomnia.
Lethargy.
Abnormal Sweating.
Changes in skin texture.
Recurrent infections.
Depression.

CRPS TYPE 2 - (Causalgia). Is caused by a nerve or tissue injury that is affected by a known ongoing abnormality (a lesion, a tumour, an AVM) - the cause of the damage does not heal or go away. The symptoms are the same as
in Type 1 (RSD).

Who gets CRPS - anyone, any age, any sex, any race. What's is happening? - Ah - this is the problem - even the Medical profession is unsure as to exactly what occurs. What is currently believed is that the injured nerve starts behaving very erratically and begins to effect other totally healthy nerves. There is a condition known as 'Sympathetically Mediated Pain' - this means simply that healthy parts of the body's nervous system (the Autonomic Sympathetic Nervous System) are being abnormally activated and this actually make things worse! There are also other more complicated and alternative suggestions as to what is going on - so it is clear that, at least for the moment, we cannot be certain as to what is actually happening. However there is a lot of research going on and we must be hopeful that in the future it will be understood more.

The key difficulties at the moment are that the diagnosis is based almost entirely on the presenting symptoms alone - there is no definitive blood test, X-Ray or scan that can confirm CRPS. Indeed many traditional tests such as 'Nerve Conduction' will reveal no abnormalities as it is the microscopic nerves that are deranged - not the major nerves.
It has to be said that Doctors around the world are not in total agreement on what CRPS is, and many are not aware of it. Thus CRPS can be missed or overlooked. Alternatively - as indicated above - there are many names for it
despite attempts to bring under the term CRPS - Doctors may use other terms to describe or diagnose the syndrome - our son Sam has only ever had a formal diagnosis of "Chronic Pain Syndrome" although he has presented with
every major aspect of CRPS.

At the end of the day what it is called doesn't really matter - it is the symptoms that count!
Dave Barton - Group Organiser of SKIP (Supporting Kids In Pain)